Removing and replacing the ECU in the E9x M3 is very simple task and will only take about 30 minutes. Here’s the step by step instruction : remove the driver side air conditioning filter cover. The air conditioning filter cover is a triangular box located right in front of the firewall. Remove the three screws holding the air filter cover in place. Once removed the filter cover will still be attached by an air temperature sensor. Leave the sensor attached and just rotate the filter cover out of the way. The air temperature sensor is held on a rotating lock ficture and two compression tabs. Don’t pull on the wiring to remove the compression tabs.
Download